This invention claims the benefit of Japanese Patent Applications No. 2000-392979, filed on Dec. 25, 2000, and No. 2001-190196, filed on Jun. 22, 2001, which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a vehicle light for use as an automobile headlight, and more particularly relates to a vehicle light including a single light source capable of switching modes of a light distribution pattern between a low-beam mode and a high-beam mode by a movable shutter. The structure of the present invention is directed to a case wherein it may be difficult to have two light sources such as when an incandescent lamp or a discharge lamp is adopted as a light source of the vehicle light.
2. Description of the Related Art
FIG. 18 illustrates a conventional vehicle light 90 comprising a single light source 91a capable of switching modes of a light distribution pattern. The vehicle light 90 comprises a high intensity discharge lamp 91 such as a metal halide lamp. A discharge arc 91a of the high intensity discharge lamp 91 is the light source for the conventional vehicle light 90. The vehicle light 90 also comprises a reflector 92 of an ellipse group reflecting surface such as a rotated elliptic surface 92 having a first focus f1 on the light source 91a and a second focus f2. The vehicle light 90 further comprises a shutter 93 located in the vicinity of the second focus f2 of the ellipse group reflecting surface 92, and a projection lens 94 of a convex lens having a focus in the vicinity of the second focus f2.
Light rays emitted from the light source 91a directly to the ellipse group reflecting surface 92 are reflected thereby and converge in the vicinity of the focus f2 of the projection lens 94. Light rays travel from the ellipse group reflecting surface 92 to its second focus f2 such that the light rays collectively form luminous flux having a shape of a substantial cone with an apex approximately on the second focus f2 in a cross-section along an optical axis X of the vehicle light 90. Light rays converged in the vicinity of the second focus f2 of the ellipse group reflecting surface 92 provide a focused image of light. Since the second focus f2 of the ellipse group reflecting surface 92 is also a focus of the projection lens 94, the projection lens 94 projects the focused image of light upside down with its left side to be the right side in a forward direction while enlarging the focused image, whereby the vehicle light 90 illuminates a predetermined front area on a road. The shutter 93 can be selectively inserted in, and removed from, the cone-like luminous flux. When the shutter 93 is inserted in the luminous flux, the shutter 93 cuts off an unnecessary portion of light to form a low-beam mode light distribution pattern of the vehicle light 90. The unnecessary portion of light is typically a portion which generally illuminates in an upper right forward direction of the vehicle after being projected by the projection lens 94, which can be glare light to a driver of a car driving on an on-coming lane (when driving forward on the left side of the road). The shutter 93 in its inserted position cuts off a lower area of a chord located in a lower half of a circular cross-sectional image of the cone-like luminous flux in the vicinity of the second focus f2, thereby the remaining luminous flux provides an approximate upper half of the circular cross-section. After passing through the projection lens 94, the image of an approximate upper half of the circular cross-section becomes an image of an approximate lower half of the circular cross-section. Accordingly, a low-beam mode light distribution pattern of the vehicle light 90 is obtained.
In the high-beam mode of the vehicle light 90, the shutter 93 is removed from the cone-like luminous flux. When the shutter 93 is removed from the cone-like luminous flux, an image of light rays converged in the vicinity of the second focus f2 of the ellipse group reflecting surface 92 is substantially circular and is consistent with the circular cross-section of the cone-like luminous flux. At this time, light rays traveling in an upward direction from the vehicle light 90 are included such that a far distant front area is illuminated.
The conventional vehicle light 90 has several drawbacks, some of which include the following problems. In the low-beam mode, a substantial half of the luminous flux from the ellipse group reflecting surface 92 is cut-off by the shutter 93. Accordingly, a light amount illuminated from the vehicle light 90 is reduced to approximately half of a light amount emitted from the light source 91a. In most times of operation, the vehicle light 90 is operated in its low-beam mode due to increased traffic in recent years. Therefore, the loss of light in a low-beam mode operation has become a significant problem from viewpoints of utilization efficiency of light emitted from the light source 91a and long distance visibility of the vehicle light 90.
Further, in the conventional vehicle light 90 comprising an ellipse group reflecting surface 92, it is difficult to form a large diameter of the projection lens 94. Since the projection lens 94 converges light rays incident thereto by a predetermined degree, the illumination angle of the vehicle light 90 tends to be laterally small. Additionally, during operation of the vehicle light 90, the light emitting area of the vehicle light 90 is smaller than that of other types of conventional vehicle lights without the projection lens 94. Accordingly, visibility from a viewpoint of an on-coming vehicle or people is deteriorated in comparison with other types of conventional vehicle lights without the projection lens 94.
In order to resolve the aforementioned drawbacks and problems in the related art, the present invention provides vehicle lights that can include the following structures. In a first aspect of the present invention, a vehicle light includes a single light source capable of switching a light distribution pattern between low-beam mode and high-beam mode by a movable portion, a first reflecting surface whose longitudinal direction is along an optical axis X of the vehicle light, and having a first focus in the vicinity of the light source, for reflecting light rays from the light source forward, a projection lens, and a shutter for providing a predetermined shape to the light rays from the first reflecting surface on formation of a low-beam mode light distribution pattern by being selectively inserted in the luminous flux from the first reflecting surface to the projection lens. The vehicle light can also include a second reflecting surface of an ellipse group reflecting surface having its first focus approximately on the light source and its second focus at a predetermined position; at least one third reflecting surface having a first focus in a predetermined position and at least one second focus in at least one predetermined position; a fourth reflecting surface having a focus approximately on the second focus of the second reflecting surface for reflecting light rays in a predetermined forward direction. When the third reflecting surface is located in its inserted position relative to the luminous flux from the second reflecting surface to the fourth reflecting surface, the first focus of the at least one third reflecting surface is preferably substantially on the second focus of the second reflecting surface, and the movable portion includes the shutter and the at least one third reflecting surface.
In another aspect of the present invention, the corresponding second focus of the at least one third reflecting surface can be located in the horizontal vicinity of the focus of the first reflecting surface.
In yet another aspect of the present invention, the at least one third reflecting surface and its corresponding second focus can be located at the same side relative to the optical axis of the vehicle light.
In still another aspect of the present invention, the movable portion preferably includes an aperture or a window portion located in an area corresponding to an optical path from the second reflecting surface to the fourth reflecting surface when the at least one third reflecting surface is located in its removed position relative to the luminous flux from the second reflecting surface to the fourth reflecting surface.
In another aspect of the present invention, the vehicle light further include at least one fifth reflecting surface having a focus approximately on the corresponding second focus (or foci) of the at least one third reflecting surface for reflecting light rays forward.
In a further aspect of the present invention, each of the at least one third reflecting surfaces preferably includes at least two third reflecting surface elements, each of the at least two third reflecting surface elements having a first focus at respective predetermined positions in the vicinity of the second focus of the second reflecting surface, and a common second focus.
In yet another aspect of the present invention, the common second focus is approximately on the corresponding focus of the at least one fifth reflecting surface.
In another aspect of the present invention, the movable portion includes a rotational axis, and can be rotated around the rotational axis such that the shutter and the third reflecting surface can be inserted in or removed from their corresponding luminous flux.
In a still further aspect of the present invention, the movable portion can include a solenoid, a return spring, and a stopper.
Additional features, advantages, and embodiments of the invention may be set forth or apparent from consideration of the following detailed description, drawings, and claims. Moreover, it is to be understood that both the foregoing summary of the invention and the following detailed description are exemplary and intended to provide further explanation without limiting the scope of the invention as claimed.